Process of recovering zinc from brass scrap and other materials containing zinc



Patented Aug. 15, 1933 ummfsn PROCESS OF RECOVERING "ZINC FROM BRASS SCRAP AND CONTAINING, zINc 1 William J. OBrien,

Cleveland OTHER MATERIALS ohm, and Joseph E. Drapeau, Jr., NewYork, N. Y., assignors to The Glidden Company,

' poration of Ohio Cleveland, Ohio, a Cor- No Drawing. Application April 20, 1931 Serial No. 1 Claim. 01. 23 -125 This invention relates to the process of recovering zinc from brass by means of'a blast furnace or converter, the treatment of the zinc with sulphuric acid and the removal of the impurities 5 from the solution and has'for its object the re-' covery of zinc with not more than a minor trace of iinpurities'which is suitable for use in the manufacture of lithopone and other products. I

In the manufacture of lithopone zinc materials I with not more than a minor trace of impurities are necessary because the lithopone mustbe' of exceptional whiteness'and must ha'velafair de-' gree of light stability; It is well known in the art thata'zinc sulphate solution containing more thanone part per million of nickel per liter of zinc sulphate solution of 35Beaum, 60 Fahrenheit temperature, will when combined with ba-- rium sulphide produce a lithopone which has a decided yellow cast. Tracesjof iron as lowas three or four parts per million per'liter of zinc sulphate solution of 35 Beaum, 60 Fahrenheit temperature, will when combined with barium sulphide produce a lithopone which has adecided Y pinkish cast. Minute traces of copper inthe zinc sulphate solution will cause" a grayish cast.

More than three tenths grains of chlorine in the zinc sulphate solution will affect the photogenic properties of the lithopone. f v 'A large supply ofzinc is available in-brass scrap but no process that we know of has been developed up to thepresent time for recovering the impurities so that saidzinc is available for the satisfactory and economical manufacture of 1 lithopone and other products requiring a zinc 5 with not more than a minor trace of impurities. In carrying out our invention secondary brass metals, such as brass scrap frcm old radiators,"j brass pipe, etc., are either baled, broken or thrown directly into the blast furnace or con-; verter, depending on the ironcontenta In conducting the operation enough'air is used to give the necessary combustion, but not sufficient air to oxidize the copper. V I j Under this treatment the 'zinc is fumed ofi first as metallic zinc, which burns in the fines to zinc oxide. Along with the zinc are carried various amounts of" other impurities,-.- such as arsenic, antim0ny,tin, lead, copper and chlorine. I V The hot fume is then carried bymeans of suitable flues through ajdust settling chamber where the coarse particles are removed mechanically, and then into a fine fume collecting systemconsisting of bags. In order'to get the'proper re-, sults not only must the quantity of air permitted --in the system be controlled, but the proper We have-f ound that a slightly acid leach is necthe liquids could befcarri the large quantity pres .phate from on v chlorine perliter, less than one part per million temperature maintained. This temperature we have found to be somewhere'between 200 and 230 Fahrenheit i I l Fromthe dust collecting equipment the mate-' rial is rundirectly into leaching tanks provided 60. with agitatori ln the leaching tanks the zinc fume is'treated with sulphuric acid. As rapid a leach as possible is made so as to avoid settling troubles. The leach is finished ofi slightly acid.-

65, essary .to prevent the loss of copper, to aid in the removal of chlorine and .to aid settling. Theyattack box operationis so carried on that the resulting zinc sulphate'solution will be approximately35 Beaum at 130 Fahrenheit and 7 will contain approximately one part of solids per ten parts of liquid.

- It was found that. because'of theeextremely colloidalnature of the resulting suspension, no

filtering operation could be successfully em ployed. However, by adjusting the proper acid conditions-which should be approximately 1%. L

iree sulphuric acid-it was found that the mate-,

rial could be settled in sufliciently large tanks so that an economic separation of the solids from 5 ed out; The resulting zinc sulphate solution contains 10 grams of acid 7 per liter, 7 grams of chlorineper liter, about 6 a I grams of copper per liter, 2 gramsof iron per liter,- 5 grams of arsenic per liter, and-varying amounts of nickel, tin, cadmium and other impurities.

Because of the complexity of the impurities'and ent, special methods of treatment are involved. The chlorine is removed as copper chloride by the addition of copper powder and copper sulphate in the proportions of one gram of copper per liter to one gram, of

chlorine. The arsenic: and part of the iron is removedby treatment with lime, after the zinc sul- 5 phate solution has been neutralized with zinc oxide. The other impurities areremoved according to well-known methods.

The resulting purified zinc sulphate solution will contain approximately 10% zinc as zinc sule-tenth to two-tenth grams of nickel, faint traces ofiron and manganese, and is suitable for lithbponemanufacture.

;.The zinc sulphate solution is pumped to a precipitating tank, combined with barium sul-' 'phide solution, and the process fromcthere on is carried out in the mannerwell known 'to those skilled inthe art of making lithopone.

minor trace of impurities,

sulphuric acid, removing chlorine by adding copper powder and copper sulphate in the proportion of one gram of copper per liter to, one gram of chlorine, neutralizing the acid solution with Zinc oxide, eliminating arsenic and part ofthe iron by treating with lime, and removing all but a minor trace of all other impurities.

WILLIAM J. OBRIEN. JOSEPH E. DRAPEAU, JR. 

